-
-Automatic Mode Selection
+
+Automatic Debugger Selection
bugpoint reads each .bc or .ll file
specified on the command line and links them together into a single module,
called the test program. If any LLVM passes are
specified on the command line, it runs these passes on the test program. If
-any of the passes crash, or if they produce a malformed LLVM module,
-bugpoint enters crash debugging mode.
+any of the passes crash, or if they produce malformed output, +bugpoint starts the crash debugger.
Otherwise, if the -output option was not specified, bugpoint runs the test program with the C backend (which @@ -53,18 +53,18 @@ is assumed to generate good code) to generate a reference output. Once executing it with the selected code generator. If the resulting output differs from the reference output, it assumes the -difference resulted from a code generator failure, and enters -code generator debugging mode.
+difference resulted from a code generator failure, and starts the +code generator debugger.
Otherwise, bugpoint runs the test program after all of the LLVM passes have been applied to it. If its output differs from the reference output, it assumes the difference resulted from a failure in one of the LLVM passes, -and enters -miscompilation debugging mode. Otherwise, +and enters the +miscompilation debugger. Otherwise, there is no problem bugpoint can debug.
-
-Next, bugpoint tries removing functions from the module, to reduce the
-size of the test program. Usually it is able to reduce a test program
+Next, bugpoint tries removing functions from the test program, to
+reduce its
+size. Usually it is able to reduce a test program
to a single function, when debugging intraprocedural optimizations. Once the
number of
functions has been reduced, it attempts to delete various edges in the control
@@ -85,36 +86,37 @@ reproduce the failure with opt or
analyze.
-
+two bytecode files (called "test" [to be compiled with the code generator] and
+"safe" [to be compiled with the C backend] respectively), and instructions for
+reproducing the problem. The code generator debugger assumes that the C
+backend produces good code.
-If you are using this mode and get an error message that says "Non-instruction
+If you are using the code generator debugger and get an error message that
+says "Non-instruction
is using an external function!", try using the -run-llc option instead
of the -run-jit option. This is due to an unimplemented feature in the
-code generator debugging mode.
+code generator debugger.Crash debugging mode
+Crash debugger
If an optimizer crashes, bugpoint will try as hard as it can to
reduce the list of passes and the size of the test program. First,
@@ -72,8 +72,9 @@ reduce the list of passes and the size of the test program. First,
is useful when debugging a problem exposed by gccas, for example,
because it runs over 25 optimizations.Code generator debugging mode
+Code generator debugger
The code generator debugger attempts to narrow down the amount of code that is
being miscompiled by the selected code generator. To do
-this, it takes the LLVM program and partitions it into two pieces: one piece
+this, it takes the test program and partitions it into two pieces: one piece
which it compiles with the C backend (into a shared object), and one piece which
it runs with either the JIT or the static LLC compiler. It uses several
techniques to reduce the amount of code pushed through the LLVM code generator,
to reduce the potential scope of the problem. After it is finished, it emits
-two bytecode files (the "test" [to be compiled with the code generator] and
-"safe" [to be compiled with the C backend] modules), and instructions for
-reproducing the problem. This module assume the C backend produces good
-code.